2000rpm Fail Safe on 1987 Yamaha 115hp motor

[Richie]

I hope someone may be able to help me out here. I inherited a 1987 Ranger with a 115hp Yamaha motor. Went out in it and wouldnt run over 2000rpm. Having the manual on it, I read over it and seen where certain things can cause the 2000rpm fail safe. After cleaning out the oil, refilling and making sure it pumps right, and making sure the water was pumping correctly, (ie coming out the pee hole), set it up and fired the boat on land using water muffs. In gear it would run over the 2000rpm. Put it in the water, hit the throttle, no go, droped back to the 2000rpm fail safe. Made sure there that everything was still functioning correctly. Still no more than 2000rpm, if I tried to give it more it would choke out. Bringing it back to the shop, put the muffs back on it, started it up put it in gear, run over the 2000rpm mark. Checked to make sure all the alarms worked properly that would trigger the 2000rpm Fail safe. Finally decided to try one last thing, still on the muffs, ran the engine at 3500rpm, I pulled the oil sensor unit out of the oil tank, the engine did not go into the 2000rpm fail safe like it should. This I dont understand, it will go into it when in the water, but ont he muffs it will not. Anyone know why this is? Is there a sensor I am missing? Also does anyone else know what my problem may be why it stayes in the fail safe mode in the water?

Any Help is greatly appreciated.

Richie

[Hamfisted]

Does the alarm horn work? Is it going off when the rpm reduction occurs? If not it's not in the "Safe" mode. There's something else wrong. Can you pump up the fuel primer ball firm? If not it could be a bad fuel pump and fuel starvation. There's only one fuel pump on that motor, so it has to work right or the motor won't go. New sparkplugs?


Mike

[Bluebird]

Replace fuel pump, Pull and clean carbs, Drain out all the old fuel in the boat, Add a 10 micron racor fuel water seperator, and hang on!

[Ken]

Richie,
I agree with Hamfisted and Bluebird.
Get your boat back out on the water and up to max rpm - 2000 - and then have someone pump the primer bulb several times. If the rpms pick up, then you have a bad fuel pump. If not, then the carbs need to be torn down and cleaned and kit installed.
If the motor was allowed to set up for more than a month w/o being run, then there is a good chance the carbs are clogged with gum/varnish. High speed jets most likely.
You could try a shock treatment with SeaFoam or RingFree to clean up the carbs - sometimes that works. Or you could pull the jets and drain plugs on the carbs and squirt some Berryman's Chemtool into the orifices - sometimes that works.
If none of the above works, then remove, clean, and install a carb kit.
When your motor goes into rpm reduction mode due to either overheating or low oil, first the alarm will sound and then a few seconds later the motor will miss and shake like crazy because the ignition control has cut way back on the spark.
You throttle back to idle and it will run smoothly until oil is added or motor cools.
Hope this helps [img]smile.gif[/img] ,
Ken K

[Richie]

Thanks for the info guys.... But still need to understand a few things. Yes the alarms will sound, atleast by closing the circuit with test wires. So I assume they are working properly. In the area of the fuel system.... why will the engine run in gear with the water muffs on it well above the 2000rpm mark. We had it up to 4000rpm last night using the muffs on dry land. But when you put it into the water, and throttle it up it will only go to 2000rpm? I still have more throttle that I can give it, but when I try to, it sounds like it loads up and dies.

Thanks

[Bluebird]

If it's like mine (86 115) it will work until you put a load on it. I think because since its only running on three (or two) cylinders it won't make enough horsepower to get the boat on plane. It goes BOGGGG flat. That motor is a runner. Do all the checks, compression, spark, pumps water, moves oil from the tanks, etc. Then clean those carbs!

[Ken]

Richie,
Out of the water with no load, the motor can easily rev up to 4000 rpm w/o any fuel from the high speed jets at all - just the low speed.
When you put it in the water and give it throttle, the load quickly "consumes" the amount of fuel from the low speed jets and then the motor has to have fuel from the high speed jets to take over and go on to higher rpm with the heavier load.
Ken K [img]smile.gif[/img]

[Richie]

Thank you to everyone that helped me out with this matter.... (Please remeber this is my first boat I ever owned) We pulled the high side jets out and cleaned them yesterday, purchased some Sea Foam and added it to the gas, also put a cap full directly into the fuel filter and ran it on dry land to knoch anything loose in the lines. We put the boat back into the water, and with a little coaxing, got the speed over 2000rpm. I am in the drivers seat, 2500rpm, doing good, 2800rpm still doing good, bow standing up in the water. We crest the 3000rpm mark, easing more into it, gave it more throttle, all of the sudden, the bow dropped back into the water, the rpms shot up to 4000rpm, scared the hell out of me, I reactively pulled back on the throttle, my friend that went with me, asked me what are you doing.... He said the look on my face was priceless, and my eyes were as wide as saucers... you see I never really understood what "plane" meant.... My friend, who has been around boats his whole life, took over and he showed me what the boat could really do, we topped out at about 55mph, at about 5200rpm. You all werent kidding when you said hold on. I did drive it again for about an hour getting it up on plane and had a great time.... We just have one little problem now that wont be too bad to fix, it doesnt want to Idle now, so we are going to go ahead and completely pull the carbs and clean them. The completion of this project had a funny ending.... I thought I would share it with you all to get a good laugh for all the help that you all gave me. Again Thank you for all the great information.

Richie